Researchers in the musculoskeletal field are increasingly using animal models of human disease,[unreadable] particularly those of tissue injury and repair. In an animal model, a factor believed to be important in the[unreadable] disease process can be administered and the response evaluated and monitored over time. Many assays[unreadable] require sacrifice of the animal in order to extract tissue for analysis; however, longitudinal studies in which[unreadable] changes in a particular animal can be evaluated in vivo and over time are often advantageous. Although both[unreadable] large and small animal disease models currently exist and are readily being developed for various human[unreadable] diseases, the use of small animals (e.g., mouse, rat) has become increasingly preferred for many reasons:[unreadable] 1) the availability of transgenic and knockout animals; 2) the ease of procuring large numbers of closely[unreadable] matched animals; and 3) animal cost, handling, housing, and other practical management issues. More[unreadable] importantly, the genome sequences of both the rat and the mouse have been deciphered, giving rise to a[unreadable] wide variety of molecular tools.[unreadable] The University of Pennsylvania has one of the most comprehensive small animal imaging facilities in[unreadable] the world that is staffed by some of the leading scientists in the various imaging modalities.[unreadable] The overall objective of this Small Animal Imaging Core is to develop and utilize a wide range of[unreadable] imaging modalities directed toward problems of musculoskeletal tissue injury and repair. The Specific Aims[unreadable] are: Aim 1: To provide guidance and expertise on the capabilities, advantages, and disadvantages of various[unreadable] imaging modalities for musculoskeletal research through formal educational enrichment programs and oneon-[unreadable] one interactions; Aim 2: To provide facilities and expert collaboration in Small Animal Imaging studies[unreadable] employing MRS/MRI, optical imaging, bioluminescence, PET/SPECT, micro-CT and/or ultrasound; Aim 3: To[unreadable] provide facilities and expert collaboration in Ancillary Facilities including chemistry (for preparation of NMR[unreadable] and optical probes), radiochemistry, molecular biology, image analysis, animal models, and biostatistics; and[unreadable] Aim 4: To provide funding for development of new projects and collaborations, and to develop preliminary[unreadable] and/or feasibility data for investigators.[unreadable] Successful completion of these aims will significantly enhance the environment and the capabilities of[unreadable] researchers at the University of Pennsylvania, leading to novel and innovative approaches to address[unreadable] musculoskeletal disorders and new collaborations between Core faculty who may have not previously[unreadable] included small animal imaging in their musculoskeletal research programs.